1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus, such as a video cassette recorder (hereinafter referred to as VCR), and more particularly to a cam gear driving apparatus driving a cam gear which operates a pinch roller assembly, a cassette loading mechanism for loading a cassette on a main base, and a tape loading mechanism for bringing a tape into contact with a head drum.
2. Description of the Prior Art
In general, an information recording and reproducing apparatus such as a VCR records video signals and audio signals on a magnetic tape which is driven through a driving system or reproduces video signals and audio signals from the magnetic tape. The VCR is divided into three types; .beta., VHS, and 8 mm according to the width of the tape on which an information is recorded. The tape is wound on a supply reel and a take-up reel provided within a cassette. When the cassette is inserted into the cassette inserting port and is mound on the VCR deck, a tape loading mechanism positions the tape from the cassette into a driving position.
The tape wound on the supply reel is drawn by a capstan and a pinch roller so as to be wound on the take-up reel. These heads are disposed between the supply reel aid the take-up reel, so that the three heads erase, record, and reproduce signals by making contact with the tape during a driving of the tape.
At this time, since the capstan and the pinch roller carry out the driving of the tape in a correct direction, the capstan an pinch roller have to rotate at a constant velocity; otherwise the heads can not record information onto the tape correctly and can not reproduce information recorded onto the tape, Also, the capstan and the pinch roller sustain a force, for example a tape tension which draws the tape, in order to maintain an equilibrium with the supply reel so that the heads can make stable contact with the tape and thereby prevent damage of the tape.
In general, operations of the cassette loading mechanism, the tape loading mechanism, and the pinch roller assembly, etc. are established by a cam gear. The cam gear has an upper cam and a lower cam respectively formed on an upper surface and a lower surface thereof, in which the upper cam is connected with the pinch roller assembly, the lower cam is connected with a relay plate assembly, and teeth of the cam gear are engaged with a front loading rack. Also, the cam gear has a mode switch operating gear at the upper surface thereof, which operates a mode switch.
FIG. 1 is a plan view of a VCR deck assembly on which is mounted a cam gear driving apparatus 10 according to the conventional art, and FIG. 2 is a perspective view of cam gear driving apparatus 10 according to the conventional art. Referring to FIGS. 1 and 2, a cam gear driving apparatus 10 according to the conventional arm includes a loading motor 40, which is supported by a supporting member 30 attached at a side of a base 20, for generating power, a driving pulley 44 mounted on a rotating shaft 42 of the loading motor 40, a driven pulley 48, which is supported by supporting member 30, for receiving power transferred through a bolt 46 front driving pulley 44, and a worm 50, which is connected at one end thereof to driver pulley 44 and is engaged with a cam gear 60, for rotating cam gear 60.
In cam gear driving apparatus 10 according to the conventional art as constructed above, when loading motor 40 is operated, a driving force is transmitted through driving pulley 44 connected to rotating shaft 42, belt 46, and driven pulley 48 to worm 50. Accordingly, cam gear 60, which is engaged with worm 50, rotates so that the pinch roller assembly, the relay plate assembly, and the front loading rack which are respectively connected to the upper cam, the lower cam, and the teeth of cam gear 60, are operated by cam gear 60.
However, there is a problem in that since cam gear driving apparatus 10 transmits the driving force of loading motor 40 through driving pulley 44, belt 46, and driven pulley 48 to worm 50, a slip may be created between driving pulley 44 and belt 46 or between driven pulley 48 and belt 46, so that a relatively high starting torque is needed to drive cam gear 60.
Also, there are other problems in that a precise finishing of teeth or worm 50 and cam gear 60 is necessary, and it is difficult, to adjust a tolerance in the assembly of worm 50 and cam gear 60.